This invention relates to methods and devices for making reaction products, and especially dibasic acids, by oxidizing a hydrocarbon under controlled conditions.
There is a plethora of references (both patents and literature articles) dealing with the formation of acids, one of the most important being adipic acid, by oxidation of hydrocarbons. Adipic acid is used to produce Nylon 66 fibers and resins, polyesters, polyurethanes, and miscellaneous other compounds.
There are different processes of manufacturing adipic acid. The conventional process involves a first step of oxidizing cyclohexane with oxygen to a mixture of cyclohexanone and cyclohexanol (KA mixture), and then oxidation of the KA mixture with nitric acid to adipic acid. Other processes include, among others, the xe2x80x9cHydroperoxide Processxe2x80x9d, the xe2x80x9cBoric Acid Processxe2x80x9d, and the xe2x80x9cDirect Synthesis Processxe2x80x9d, which involves direct oxidation of cyclohexane to adipic acid with oxygen in the presence of solvents, catalysts, and initiators or promoters.
The Direct Synthesis Process has been given attention for a long time. However, to this date it has found little commercial success. One of the reasons is that although it looks very simple at first glance, it is extremely complex in reality. Due to this complexity, one can find strikingly conflicting results, comments, and views in different references.
It is well known that after a reaction has taken place according to the Direct Synthesis, a mixture of two liquid phases is present at ambient temperature, along with a solid phase mainly consisting of adipic acid. The two liquid phases have been called the xe2x80x9cPolar Phasexe2x80x9d and the xe2x80x9cNon-Polar Phasexe2x80x9d. However, no attention has been paid so far to the importance of the two phases, except for separating the adipic acid from the xe2x80x9cPolar Phasexe2x80x9d and recycling these phases to the reactor partially or totally with or without further treatment.
It is also important to note that most studies on the Direct Oxidation have been conducted in a batch mode, literally or for all practical purposes.
There is a plethora of references dealing with oxidation of organic compounds to produce acids, such as, for example, adipic acid and/or intermediate products, such as for example cyclohexanone, cyclohexanol, cyclohexylhydroperoxide, etc.
The following references, among the plethora of others, may be considered as representative of oxidation processes relative to the preparation of diacids and intermediate products.
U.S. Pat. No. 5,463,119 (Kollar), U.S. Pat. No. 5,374,767 (Drinkard et al.), U.S. Pat. No. 5,321,157 (Kollar), U.S. Pat. No. 3,987,100 (Barnette et al.), U.S. Pat. No. 3,957,876 (Rapoport et al.), U.S. Pat. No. 3,932,513 (Russell), U.S. Pat. No. 3,530,185 (Pugi), U.S. Pat. No. 3,515,751 (Oberster et al.), U.S. Pat. No. 3,361,806 (Lidov et al.), U.S. Pat. No. 3,234,271 (Barker et al.), U.S. Pat. No. 3,231,608 (Kollar), U.S. Pat. No. 3,161,603 (Leyshon et al.), U.S. Pat. No. 2,565,087 (Porter et al.), U.S. Pat. No. 2,557,282 (Hamblet et al.), U.S. Pat. No. 2,439,513 (Hamblet et al.), U.S. Pat. No. 2,223,494 (Loder et al.), U.S. Pat. No. 2,223,493 (Loder et al.), German Patent DE 44 26 132 A1 (Kysela et al.), and PCT International Publication WO 96/03365 (Constantini et al.).
None of the above references, or any other references known to the inventors disclose, suggest or imply, singly or in combination, oxidation reactions to intermediate oxidation products under conditions subject to the intricate and critical controls and requirements of the instant invention as described and claimed.
Our U.S. Pat. Nos. 5,580,531, 5,558,842, 5,502,245, as well as our PCT International Publication WO 96/40610 describe methods and apparatuses relative to controlling reactions in atomized liquids.
As aforementioned, the present invention relates to methods and devices of oxidizing a hydrocarbon, such as cyclohexane for example, to an acid, such as adipic acid for example. More particularly this invention pertains to a method of controlling in a first reaction zone the oxidation of a hydrocarbon to form an acid in the presence of a catalyst, a solvent, an optional initiator, water, and oxidation products; the hydrocarbon, the catalyst, the solvent, and at least part of the oxidation products forming at least partially a liquid mixture, the method characterized by the steps of:
(a) contacting the liquid mixture with a gaseous oxidant in the first reaction zone at a first temperature, the first temperature being adequately high for the oxidation to proceed;
(b) driving the oxidation to a steady state at a first hydrocarbon level, a first solvent level, a first catalyst level, and a first water level;
(c) controlling at least one of the first hydrocarbon level, the first solvent level, the first catalyst level, and the first water level, in a manner to cause formation of and/or maintain a single liquid phase in the first reaction zone, regardless of the presence or absence of a solid phase, and if necessary; and
(d) making phase-related adjustments to the liquid mixture, the phase-related adjustments being at least partially based on phase formation relationships, when said liquid mixture is at a second temperature, and wherein the phase related adjustments are directed toward formation and/or maintenance of a single liquid phase.
The second temperature is preferably substantially the same as the first temperature. However, it may be different than the first temperature.
The phase related adjustments to the liquid mixture in the first reaction zone may be conducted by variable selected from a group consisting of temperature in the first reaction zone, pressure in the first reaction zone, gaseous oxidant flow rate into the first reaction zone, water flow rate into the first reaction zone, water removal rate from the first reaction zone, catalyst flow rate into the first reaction zone, hydrocarbon flow rate into the first reaction zone, hydrocarbon removal rate from the first reaction zone, solvent flow rate into the first reaction zone, solvent removal rate from the first reaction zone, recycled off-gas flow rate into the first reaction zone, and a combination thereof.
It is preferable that the method comprises a step of determining, one or more of:
a maximum hydrocarbon level, a maximum water level, and a maximum catalyst level, at or over which, the single liquid phase is transformed to two liquid phases; and
a minimum solvent level, at or under which, the single liquid phase is transformed to two liquid phases;
under a set of conditions, wherein levels not being determined remain constant.
The step of determining one or more of the levels, at or over which, the single liquid phase is transformed to two liquid phases, may further comprise steps of:
obtaining a sample of a liquid mixture from the first reaction zone; and
adding to the sample, hydrocarbon, or water, or catalyst, or a combination thereof, until a second liquid is formed.
The first hydrocarbon level, the first water level, and the first catalyst level are preferably controlled to be under the maximum hydrocarbon level, the maximum water level, and the maximum catalyst level, respectively, and the first solvent level is controlled to be maintained over the minimum solvent level.
The sample may be analyzed to obtain compositional data of the sample, and therefore of the contents of the reaction zone.
The compositional data of the sample may be compared with one or more of phase diagrams, thermodynamic data bases, flow sheets, computer flow sheet simulations, catalyst precipitation data, energy balances, and experimental data, and a step of making phase related adjustments and/or catalyst precipitation adjustments may be made in order to avoid formation of a second liquid phase, and/or catalyst precipitation, respectively, in the first reaction zone, if the comparison indicates that formation of a second liquid phase and/or catalyst precipitation are being approached.
The compositional data of the sample may also be compared with one or more of the maximum hydrocarbon level, the maximum water level, the maximum catalyst level, and the minimum solvent level, and then phase related adjustments may be made in the first reaction zone, if one or more of the maximum hydrocarbon level, the maximum water level, the maximum catalyst level, and the minimum solvent level, respectively, is being approached. If the additional hydrocarbon, or water, or catalyst necessary for formation of a second liquid phase is less than 10% by weight of the total hydrocarbon, or water, or catalyst contained in reaction zone or a sample from the reaction zone, then the maximum level of hydrocarbon or water or catalyst is being approached, and corrective measures have to be taken. Examples of such corrective measures are to reduce the first hydrocarbon level or the first water level or the first catalyst level, or increase the first solvent level, or a combination thereof. It is preferable that the additional hydrocarbon, or water, or catalyst necessary for formation of a second liquid phase should be controlled to be more than 10% (and in some casesxe2x80x94more than 20%) by weight of the total hydrocarbon or water or catalyst, respectively, contained in the reaction zone or a sample taken therefrom.
One or more of the first hydrocarbon level, the first catalyst level, and the first water level may be controlled to be maintained within a majority range, or a minority range. The majority range is defined as a range between a predetermined high majority level and a predetermined low majority level, the high majority level being lower than a maximum level at or over which maximum level a second phase is formed, the low majority level being between the high majority level and an average of the maximum level and a minimum level, at and under which minimum level catalyst recipitates. It is also preferable that the high majority level is close to the level at which a second phase formation is being approached.
In other occasions, it may be preferable that the first water and/or the first solvent level is controlled to be maintained within a minority range, the minority range being a range between a predetermined low minority level, and a predetermined high minority level, the low minority level being higher than a minimum level at or under which catalyst precipitates, and the high minority level being between the low minority level and an average of the minimum level and a maximum level, at and over which maximum level a second phase is formed.
The high importance of controlling the miscellaneous levels within the majority and/or minority ranges, is that within these ranges unintentional and/or accidental formation of a second liquid phase or catalyst precipitation is minimized, if not eliminated. Depending on each individual case, and the degree of achievable control, the majority and minority high and low levels may be predetermined.
The first temperature may be controlled by evaporating condensible volatile matter from the reaction zone, and recirculating at least part of the condensible volatile matter to the reaction zone as condensate.
The methods and devices of the present invention are particularly suitable in the case that the acid comprises adipic acid, the hydrocarbon comprises cyclohexane, the solvent comprises acetic acid, the catalyst comprises a cobalt salt, and the optional initiator comprises a compound selected from a group comprising acetaldehyde, cyclohexanone, and a combination thereof.
The methods of this invention may also comprise a step of controlling at least one level of the first water level, and the first solvent level in a manner to be higher than a respective level, at or under which, catalyst precipitates; and
the first hydrocarbon level, and the first catalyst level to be lower than a respective level, at or over which, catalyst precipitates.
The above methods may further comprise steps of:
taking a sample from the first reaction zone;
lowering the temperature of the sample to a predetermined second temperature, and if a second liquid phase is formed at a critical temperature in the range between the first and second temperatures,
either decrease in the first reaction zone the first level of one component selected from a group consisting of hydrocarbon, water, catalyst, and a mixture thereof to a degree that in a new sample a second liquid phase does not form in the range between the first and second temperatures, or
increase in the first reaction zone the first solvent level to a degree that in a new sample a second liquid phase does not form in the range between the first and second temperatures, or
increase in the first reaction zone the first temperature to a third temperature by at least the difference between the critical temperature and the second temperature, or
a combination thereof.
It is preferable that controlling the first water level within the upper and lower limits (maximum water level over which a second liquid phase forms, and minimum water levels under which catalyst precipitates, respectively) is based on determining the composition of the single-phase liquid mixture of the first reaction zone, comparing said composition with one or more of phase diagrams, thermodynamic data bases, flow sheets, computer flow sheet simulations, catalyst precipitation data, energy balances, and experimental data, and adding water to the single-phase liquid mixture in the first reaction zone if the lower limit is being approached or removing water from the first reaction zone if the upper limit is being approached.
The methods of this invention may also comprise a combination of the following steps:
taking a sample from the first reaction zone;
confining the sample within a closed cell under adequate pressure to retain the sample in a substantially liquid form;
raising the cell temperature from the first temperature to a higher temperature; and if catalyst precipitates within a predetermined rise in temperature;
raising the level of water or the level of solvent in the first reaction zone, or lowering the level of hydrocarbon or the level of catalyst in the first reaction zone.
In a different version of the instant invention, the methods may comprise a combination of the following steps:
taking a sample from the first reaction zone;
confining the sample within a closed cell under adequate pressure to retain the sample in a substantially liquid form;
adding hydrocarbon to the sample to determine if catalyst precipitates before formation of a second phase; and
controlling in the first reaction zone the first hydrocarbon level to be maintained at a level lower than the level required to cause catalyst precipitation at levels of solvent, catalyst, and water present in the cell.
The methods of this invention may also comprise steps of:
lowering the first temperature of the reaction mixture to a second temperature, while maintaining a single liquid phase at the second temperature; and
removing at least part of the formed acid.
The above method may further include the step of recycling at least part of one or more of products, intermediates, by-products, reactants, solvents, off-gases, and other existing ingredients either directly to the first reaction zone or indirectly after post-treatment, or a combination thereof.
The lowering of the first temperature of the reaction mixture to the second temperature may be performed at least partially by an operation selected from a group consisting of: (a) evaporating of at least part of the hydrocarbon, (b) lowering the first pressure to a second pressure, (c) adding matter having a temperature lower than the first temperature, (d) adding volatile matter, such as cyclohexane for example, (e) removing heat by external means, (f) removing a first amount of heat by any suitable means, and adding a second amount of heat by external means, the first amount of heat being greater than the second amount of heat, and (g) a combination thereof.
Maintaining a single liquid phase at the second temperature may be controlled by adjusting the level of hydrocarbon, or water, or solvent, or a combination thereof, at the second temperature. The lowering of the first temperature to a second temperature may be preferably conducted in a second zone. The lowering of the first temperature to the second temperature may involve an intermediate step of lowering the first temperature to a first intermediate temperature by lowering the first pressure to an intermediate pressure to form a first intermediate liquid phase containing no substantial amount of solid phase.
The methods and devices of the present invention are particularly suitable in the case that the acid comprises adipic acid, the hydrocarbon comprises cyclohexane, the solvent comprises acetic acid, the catalyst comprises a cobalt salt, and the optional initiator comprises a compound selected from a group comprising acetaldehyde, cyclohexanone, and a combination thereof.
At least part of one or more of products, intermediates, by-products, reactants, solvents, off-gases, and other existing ingredients may be recycled either directly to the first reaction zone or indirectly after post-treatment, or in a combination thereof.
In any of the above-recited methods, there may be further included the step of comparing compositional data of the liquid mixture with one or more of phase diagrams, thermodynamic data bases, flow sheets, computer flow sheet simulations, catalyst precipitation data, energy balances, and experimental data, and a step of making phase related adjustments and/or catalyst precipitation adjustments in order to avoid formation of a second liquid phase, and/or catalyst precipitation, respectively, in the first reaction zone, if the comparison indicates that formation of a second liquid phase and/or catalyst precipitation are being approached.
In any of the above-recited methods, there may further include the step of reacting adipic acid with a reactant selected from a group consisting of a polyol, a polyamine, and a polyamide in a manner to form a polymer of a polyester, or a polyamide, or a (polyimide and/or poyamideimide), respectively. The invention may further include the step of spinning the polymer into fibers.
The instant invention also relates to a reactor device for oxidizing a hydrocarbon, the hydrocarbon being at least partially in a liquid state, with a gaseous oxidant to form an acid, the device comprising:
a first reaction chamber;
a temperature monitor connected to the reaction chamber for measuring temperature inside said reaction chamber;
phase detection means for detecting phase-related characteristics of ingredients within the first reaction chamber; and
phase control means for making phase-related adjustments and controlling the phase characteristics of said ingredients within the first reaction chamber, if so desired.
The phase control means may further comprise temperature control means for controlling the first temperature. The phase control means may further comprise correlation means for correlating compositional data of the liquid mixture with one or more of phase diagrams, thermodynamic data bases, flow sheets, computer flow sheet simulations, catalyst precipitation data, energy balances, and experimental data, and making phase related adjustments and/or catalyst precipitation adjustments in order to avoid formation of a second liquid phase, and/or catalyst precipitation, respectively, in the first reaction zone, if the correlation indicates that formation of a second liquid phase and/or catalyst precipitation are being approached.
The phase detection means may provide information to the phase control means for adjusting feeding rates of ingredients fed to the reaction chamber toward formation or maintenance of a single liquid phase.
The reactor device of the present invention may also comprise variable control means for controlling in the reaction chamber a variable selected from a group consisting of temperature in the first reaction chamber, pressure in the first reaction chamber, gaseous oxidant flow rate into the first reaction chamber, water flow rate into the first reaction chamber, water removal rate from the first reaction chamber, catalyst flow rate into the first reaction chamber, hydrocarbon flow rate into the first reaction chamber, hydrocarbon removal rate from the first reaction chamber, solvent flow rate into the first reaction chamber, solvent removal rate from the first reaction chamber, recycled off-gas flow rate into the first reaction chamber, and a combination thereof.
The reactor device may also comprise:
liquid feeding means for feeding at least partially hydrocarbon, solvent, catalyst, optionally initiator, and optionally water into the first reaction chamber;
water removing means for removing water from the first reaction chamber;
gaseous feeding means for feeding oxidant into the first reaction chamber; and
water level control means for controlling the water level in the reaction chamber in a range between a maximum level of water, over which maximum level the substantially single liquid phase is transformed to two liquid phases, and a minimum level under which catalyst precipitates.
The water level control means may comprise water level detection means for detecting positioning of the water level with respect to the maximum level and the minimum level.
The reactor device may also comprise a controller connected to the water level detection means for receiving information regarding the positioning of the water level, and using said information for adjusting said water level in a manner to control said water level between the maximum level and the minimum level in the reaction zone.
The water level detection means may comprise a temperature operated detector, or a water-addition operated detector, or both for detecting the positioning of the water level with respect to the minimum level and the maximum level, respectively. Further, the water level control means may comprise an analytical water level detection means for detecting and/or determining the water level in the first reaction chamber, and wherein the reactor device further comprises a controller connected to the analytical water level detection means for receiving information regarding the water level in the reaction chamber, comparing said information with one or more of phase diagrams, thermodynamic data bases, flow sheets, computer flow sheet simulations, catalyst precipitation data, energy balances, and experimental data stored in the controller, and using said comparison for adjusting said water level in the first reaction chamber in a manner to control said water level between the maximum level and the minimum level.
The reactor device may further comprise a distillation column or a condenser, connected to an off-gas line exiting the first reaction chamber. A decanter or retaining chamber may be connected to the condenser.
The water level detection means may comprise a temperature operated detector for detecting the positioning of the water level with respect to the minimum level, and/or a water-addition operated detector for detecting the positioning of the water level with respect to the maximum level.
The reactor device may also comprise:
first temperature control means connected to the first reaction chamber for controlling temperature in said first reaction chamber;
first pressure control means connected to the first reaction chamber for controlling pressure in said first reaction chamber;
first hydrocarbon feeding means connected to the first reaction chamber for feeding hydrocarbon into said first reaction chamber;
first gaseous oxidant feeding means connected to the first reaction chamber for feeding gaseous oxidant into said first reaction chamber;
a second chamber connected to the first reaction chamber;
second temperature control means connected to the second chamber for controlling the temperature in said second chamber;
second pressure control means connected to the second chamber for controlling the pressure in said second chamber;
a controller for controlling miscellaneous parameters in the chambers in a manner that in the second chamber there is a single liquid phase.
A condenser(s) or distillation column(s) may be connected to the first reaction chamber and to the second chamber. A retaining chamber(s) or decanter(s) may be connected to the condenser(s).
The reactor device may further comprise a first intermediate chamber communicating with the first reaction chamber;
a first intermediate chamber communicating with the first reaction chamber;
first intermediate temperature control means connected to the first intermediate chamber for controlling the temperature in said first intermediate chamber;
first intermediate pressure control means connected to the intermediate chamber for controlling the pressure in said first intermediate chamber;
first intermediate external heating means for providing thermal energy to matter inside the first intermediate chamber;
a condenser connected to the first intermediate chamber;
separating means connected to or being part of the second chamber for separating at least partially the dibasic acid from the mixture.
It may further comprise:
a second intermediate chamber connected to the first intermediate chamber and the second chamber;
second intermediate external cooling means for removing thermal energy from matter inside the second intermediate chamber.
A second phase control means may be connected to the second chamber for ensuring the existence of one single liquid phase in the second chamber. Also, a catalyst precipitation control means may be connected to the second chamber for ensuring the absence of precipitated catalyst in the second chamber.
Under certain circumstances, at least two of the chambers may be one and the same unit.
One or more of the reaction chambers or other chambers, may be of the atomization or the stirred-reactor type.
In any of the above described chambers, means for adding heat by internal or external means, removing heat by internal or external means, adding volatile matter, removing volatile matter, controlling temperature, controlling pressure, etc., may be incorporated.
In the embodiments described herein, the amount of water present includes amounts of water introduced by other means, such as the crystalline water of cobalt(II) acetate tetrahydrate, for example, unless otherwise specified. In the case that the water, such as crystalline water for example, is not accounted for as being part of the water level, then it is accounted for as being part of the entity that it introduces it, such as catalyst for example. This invention encompasses both cases. Control may be achieved by either taking into account additional water, such as for example the crystalline water of the catalyst, or by not accounting for such additional water, depending on the particular situation.
By the term xe2x80x9csteady statexe2x80x9d it is meant that the reaction has reached an equilibrium, which equilibrium, however, may be adjusted periodically or continuously in order to achieve a desired result. If for example more water is needed in the reaction zone to avoid catalyst precipitation, the water feed rate to the reaction zone may be increased appropriately, and still the reaction may be considered to be at a xe2x80x9csteady statexe2x80x9d. Similarly, if less water is needed to avoid formation of two phases, the water feed rate to the reaction zone may be decreased appropriately, and still the reaction may be considered to be at a xe2x80x9csteady statexe2x80x9d.
The terms xe2x80x9csubstantially single-phase liquidxe2x80x9d, xe2x80x9csubstantially single liquid phasexe2x80x9d xe2x80x9csingle liquid phasexe2x80x9d, and xe2x80x9csingle phasexe2x80x9d are for all practical purposes synonymous for the purposes of this invention. They all intend to indicate that there is no second liquid phase present, while a solid phase may or may not be present. The terms xe2x80x9csecond phase formationxe2x80x9d or xe2x80x9cformation of a second phasexe2x80x9d refer to a second liquid phase, and not to a solid phase, unless otherwise specified.
The term xe2x80x9clevelxe2x80x9d of an ingredient (reactant, reaction product, inert matter, or any other type of matter present) includes both xe2x80x9crelative levelxe2x80x9d and xe2x80x9cpercentage levelxe2x80x9d. According to the instant invention, both methods and devices may perform by using either one or the other type of xe2x80x9clevelsxe2x80x9d. In some occasions it may be easier to use one type rather than the other. xe2x80x9cRelative levelxe2x80x9d of an ingredient denotes the amount of the ingredient present in weight units or in volume units, in a reaction zone or in a cell for example, as compared to 100 units, in weight units or in volume units, respectively, of the rest of the ingredients present, or the rest of the ingredients under consideration. The rest of the ingredients present or the rest of the ingredients under consideration, in this case, have a constant ratio with respect to each other. On the other hand, xe2x80x9cpercentage levelxe2x80x9d is the level expressed as a percentage based on total amount of all or of a desired number of specific ingredients. The percentages may be expressed also either by weight or by volume.
A controller, preferably a computerized controller, may handle with ease and accuracy either type of xe2x80x9clevelxe2x80x9d. Programming a computerized controller to perform such functions is a routine process, well known to the art. According to this invention, a controller, based on information received, from a reaction zone for example, controls feed rates, temperatures, pressures, and other parameters in order to achieve the desirable results. Since the raw results regarding the point of a second liquid phase formation (which results are received from a cell, such as the cells shown in FIGS. 2, 2A, and 2B, which will be discussed in detail at a later section) are obtained in relative levels, maintenance or adjustments in the reaction zone are more accurate when xe2x80x9crelative levelsxe2x80x9d are used. The controller may also be programmed, by well known to the art techniques, to include flow sheet simulation, which may account for vapor/liquid equilibrium and energy balance effects.